added sending level file (and level template) for network games

added sending level file (and level template) for network games

As the level to play may not exist on the receiving side (but only on
the sending side -- the client who initiates the network game), this
change adds sending the level file (and the level template, if needed)
to all receiving network clients, so all clients always play the exact
same level (and do not have to worry about having the same level sets).